// Copyright (c) 2010-2014 SharpDX - Alexandre Mutel
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// -----------------------------------------------------------------------------
// Original code from SlimMath project. http://code.google.com/p/slimmath/
// Greetings to SlimDX Group. Original code published with the following license:
// -----------------------------------------------------------------------------
/*
* Copyright (c) 2007-2011 SlimDX Group
* 
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* 
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

using System;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace SharpDX
{
    /// <summary>
    /// Represents a three dimensional line based on a point in space and a direction.
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct Ray : IEquatable<Ray>, IFormattable
    {
        /// <summary>
        /// The position in three dimensional space where the ray starts.
        /// </summary>
        public Vector3 Position;

        /// <summary>
        /// The normalized direction in which the ray points.
        /// </summary>
        public Vector3 Direction;

        /// <summary>
        /// Initializes a new instance of the <see cref="Ray"/> struct.
        /// </summary>
        /// <param name="position">The position in three dimensional space of the origin of the ray.</param>
        /// <param name="direction">The normalized direction of the ray.</param>
        public Ray(Vector3 position, Vector3 direction)
        {
            this.Position = position;
            this.Direction = direction;
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a point.
        /// </summary>
        /// <param name="point">The point to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Vector3 point)
        {
            return Collision.RayIntersectsPoint(ref this, ref point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="Ray"/>.
        /// </summary>
        /// <param name="ray">The ray to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Ray ray)
        {
            Vector3 point;
            return Collision.RayIntersectsRay(ref this, ref ray, out point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="Ray"/>.
        /// </summary>
        /// <param name="ray">The ray to test.</param>
        /// <param name="point">When the method completes, contains the point of intersection,
        /// or <see cref="Vector3.Zero"/> if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Ray ray, out Vector3 point)
        {
            return Collision.RayIntersectsRay(ref this, ref ray, out point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="Plane"/>.
        /// </summary>
        /// <param name="plane">The plane to test</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Plane plane)
        {
            float distance;
            return Collision.RayIntersectsPlane(ref this, ref plane, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="Plane"/>.
        /// </summary>
        /// <param name="plane">The plane to test.</param>
        /// <param name="distance">When the method completes, contains the distance of the intersection,
        /// or 0 if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Plane plane, out float distance)
        {
            return Collision.RayIntersectsPlane(ref this, ref plane, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="Plane"/>.
        /// </summary>
        /// <param name="plane">The plane to test.</param>
        /// <param name="point">When the method completes, contains the point of intersection,
        /// or <see cref="Vector3.Zero"/> if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Plane plane, out Vector3 point)
        {
            return Collision.RayIntersectsPlane(ref this, ref plane, out point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a triangle.
        /// </summary>
        /// <param name="vertex1">The first vertex of the triangle to test.</param>
        /// <param name="vertex2">The second vertex of the triangle to test.</param>
        /// <param name="vertex3">The third vertex of the triangle to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Vector3 vertex1, ref Vector3 vertex2, ref Vector3 vertex3)
        {
            float distance;
            return Collision.RayIntersectsTriangle(ref this, ref vertex1, ref vertex2, ref vertex3, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a triangle.
        /// </summary>
        /// <param name="vertex1">The first vertex of the triangle to test.</param>
        /// <param name="vertex2">The second vertex of the triangle to test.</param>
        /// <param name="vertex3">The third vertex of the triangle to test.</param>
        /// <param name="distance">When the method completes, contains the distance of the intersection,
        /// or 0 if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Vector3 vertex1, ref Vector3 vertex2, ref Vector3 vertex3, out float distance)
        {
            return Collision.RayIntersectsTriangle(ref this, ref vertex1, ref vertex2, ref vertex3, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a triangle.
        /// </summary>
        /// <param name="vertex1">The first vertex of the triangle to test.</param>
        /// <param name="vertex2">The second vertex of the triangle to test.</param>
        /// <param name="vertex3">The third vertex of the triangle to test.</param>
        /// <param name="point">When the method completes, contains the point of intersection,
        /// or <see cref="Vector3.Zero"/> if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Vector3 vertex1, ref Vector3 vertex2, ref Vector3 vertex3, out Vector3 point)
        {
            return Collision.RayIntersectsTriangle(ref this, ref vertex1, ref vertex2, ref vertex3, out point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingBox"/>.
        /// </summary>
        /// <param name="box">The box to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingBox box)
        {
            float distance;
            return Collision.RayIntersectsBox(ref this, ref box, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingBox"/>.
        /// </summary>
        /// <param name="box">The box to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(BoundingBox box)
        {
            return Intersects(ref box);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingBox"/>.
        /// </summary>
        /// <param name="box">The box to test.</param>
        /// <param name="distance">When the method completes, contains the distance of the intersection,
        /// or 0 if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingBox box, out float distance)
        {
            return Collision.RayIntersectsBox(ref this, ref box, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingBox"/>.
        /// </summary>
        /// <param name="box">The box to test.</param>
        /// <param name="point">When the method completes, contains the point of intersection,
        /// or <see cref="Vector3.Zero"/> if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingBox box, out Vector3 point)
        {
            return Collision.RayIntersectsBox(ref this, ref box, out point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingSphere"/>.
        /// </summary>
        /// <param name="sphere">The sphere to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingSphere sphere)
        {
            float distance;
            return Collision.RayIntersectsSphere(ref this, ref sphere, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingSphere"/>.
        /// </summary>
        /// <param name="sphere">The sphere to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(BoundingSphere sphere)
        {
            return Intersects(ref sphere);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingSphere"/>.
        /// </summary>
        /// <param name="sphere">The sphere to test.</param>
        /// <param name="distance">When the method completes, contains the distance of the intersection,
        /// or 0 if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingSphere sphere, out float distance)
        {
            return Collision.RayIntersectsSphere(ref this, ref sphere, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="BoundingSphere"/>.
        /// </summary>
        /// <param name="sphere">The sphere to test.</param>
        /// <param name="point">When the method completes, contains the point of intersection,
        /// or <see cref="Vector3.Zero"/> if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingSphere sphere, out Vector3 point)
        {
            return Collision.RayIntersectsSphere(ref this, ref sphere, out point);
        }

        /// <summary>
        /// Calculates a world space <see cref="Ray"/> from 2d screen coordinates.
        /// </summary>
        /// <param name="x">X coordinate on 2d screen.</param>
        /// <param name="y">Y coordinate on 2d screen.</param>
        /// <param name="viewport"><see cref="ViewportF"/>.</param>
        /// <param name="worldViewProjection">Transformation <see cref="Matrix"/>.</param>
        /// <returns>Resulting <see cref="Ray"/>.</returns>
        public static Ray GetPickRay(int x, int y, ViewportF viewport, Matrix worldViewProjection)
        {
            var nearPoint = new Vector3(x, y, 0);
            var farPoint = new Vector3(x, y, 1);

            nearPoint = Vector3.Unproject(nearPoint, viewport.X, viewport.Y, viewport.Width, viewport.Height, viewport.MinDepth,
                                        viewport.MaxDepth, worldViewProjection);
            farPoint = Vector3.Unproject(farPoint, viewport.X, viewport.Y, viewport.Width, viewport.Height, viewport.MinDepth,
                                        viewport.MaxDepth, worldViewProjection);

            Vector3 direction = farPoint - nearPoint;
            direction.Normalize();

            return new Ray(nearPoint, direction);
        }

        /// <summary>
        /// Tests for equality between two objects.
        /// </summary>
        /// <param name="left">The first value to compare.</param>
        /// <param name="right">The second value to compare.</param>
        /// <returns><c>true</c> if <paramref name="left"/> has the same value as <paramref name="right"/>; otherwise, <c>false</c>.</returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public static bool operator ==(Ray left, Ray right)
        {
            return left.Equals(ref right);
        }

        /// <summary>
        /// Tests for inequality between two objects.
        /// </summary>
        /// <param name="left">The first value to compare.</param>
        /// <param name="right">The second value to compare.</param>
        /// <returns><c>true</c> if <paramref name="left"/> has a different value than <paramref name="right"/>; otherwise, <c>false</c>.</returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public static bool operator !=(Ray left, Ray right)
        {
            return !left.Equals(ref right);
        }

        /// <summary>
        /// Returns a <see cref="System.String"/> that represents this instance.
        /// </summary>
        /// <returns>
        /// A <see cref="System.String"/> that represents this instance.
        /// </returns>
        public override string ToString()
        {
            return string.Format(CultureInfo.CurrentCulture, "Position:{0} Direction:{1}", Position.ToString(), Direction.ToString());
        }

        /// <summary>
        /// Returns a <see cref="System.String"/> that represents this instance.
        /// </summary>
        /// <param name="format">The format.</param>
        /// <returns>
        /// A <see cref="System.String"/> that represents this instance.
        /// </returns>
        public string ToString(string format)
        {
            return string.Format(CultureInfo.CurrentCulture, "Position:{0} Direction:{1}", Position.ToString(format, CultureInfo.CurrentCulture),
                Direction.ToString(format, CultureInfo.CurrentCulture));
        }

        /// <summary>
        /// Returns a <see cref="System.String"/> that represents this instance.
        /// </summary>
        /// <param name="formatProvider">The format provider.</param>
        /// <returns>
        /// A <see cref="System.String"/> that represents this instance.
        /// </returns>
        public string ToString(IFormatProvider formatProvider)
        {
            return string.Format(formatProvider, "Position:{0} Direction:{1}", Position.ToString(), Direction.ToString());
        }

        /// <summary>
        /// Returns a <see cref="System.String"/> that represents this instance.
        /// </summary>
        /// <param name="format">The format.</param>
        /// <param name="formatProvider">The format provider.</param>
        /// <returns>
        /// A <see cref="System.String"/> that represents this instance.
        /// </returns>
        public string ToString(string format, IFormatProvider formatProvider)
        {
            return string.Format(formatProvider, "Position:{0} Direction:{1}", Position.ToString(format, formatProvider),
                Direction.ToString(format, formatProvider));
        }

        /// <summary>
        /// Returns a hash code for this instance.
        /// </summary>
        /// <returns>
        /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table. 
        /// </returns>
        public override int GetHashCode()
        {
            unchecked
            {
                return (Position.GetHashCode() * 397) ^ Direction.GetHashCode();
            }
        }

        /// <summary>
        /// Determines whether the specified <see cref="Vector4"/> is equal to this instance.
        /// </summary>
        /// <param name="value">The <see cref="Vector4"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="Vector4"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public bool Equals(ref Ray value)
        {
            return Position == value.Position && Direction == value.Direction;
        }

        /// <summary>
        /// Determines whether the specified <see cref="Vector4"/> is equal to this instance.
        /// </summary>
        /// <param name="value">The <see cref="Vector4"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="Vector4"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        [MethodImpl((MethodImplOptions)0x100)] // MethodImplOptions.AggressiveInlining
        public bool Equals(Ray value)
        {
            return Equals(ref value);
        }

        /// <summary>
        /// Determines whether the specified <see cref="System.Object"/> is equal to this instance.
        /// </summary>
        /// <param name="value">The <see cref="System.Object"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="System.Object"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public override bool Equals(object value)
        {
            if (!(value is Ray))
                return false;

            var strongValue = (Ray)value;
            return Equals(ref strongValue);
        }
    }
}